Piping structure for transporting a fuel

ABSTRACT

A piping structure for transporting a fuel arranged between an engine and a fuel tank, is constructed by use of a resin tube that is formed in a straight tubular shape. The resin tube is flexed and bent at one or more points along a longitudinal direction of the resin tube to define one or more bent portions and thereby is provided with a predetermined bent shape. The resin tube is fixed in a motor vehicle body so as to retain the bent portions and thereby assembled in the motor vehicle body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piping structure for transporting afuel, a resin tube for transporting a fuel adapted in the pipingstructure, and a method for producing the resin tube.

2. Description of the Related Art

Previously, a resin tube is used for transporting a fuel, for example,transporting a fuel in a fuel tank to an engine side.

The resin tube is connected to a mating pipe on a motor vehicle bodyside to constitute a piping system for transporting a fuel.

Previously, for connecting the resin tube with the mating pipe, aconnector (quick connector) that permits simple and quick connectionwith the mating pipe has been used.

The connector of such type is disclosed, for example, in Patent Document1 below. FIGS. 12 and 13 show an example of specific construction of theconnector.

In FIGS. 12 and 13, reference numeral 200 indicates a resin tube,reference numeral 202 indicates a mating pipe to be connected with theresin tube 200.

The mating pipe 202 is formed with an engaging projection (pipe-sideengaging portion) 204 projecting annularly on an outer peripheralsurface thereof.

Reference numeral 206 indicates a connector that has a connector body(here, entirely made of resin) 208, a retainer 210, a bush 214 andO-rings 212 as sealing member.

The connector body 208 includes a retainer holding portion 216 on oneend of the connector body 208 along an axial direction (a proximal endor an axially outer end of the connector body 208), and a press-fitportion (nipple portion) 218 on the other end thereof along the axialdirection (a distal end or an axially inner end thereof) as connectingportion to the resin tube 200.

The press-fit portion 218 is a portion to be press-fitted orforce-fitted within the resin tube 200 in an axial direction. Thepress-fit portion 218 is formed with annular ribs 220 at a plurality ofaxially spaced positions on an outer peripheral surface thereof. Theannular rib 220 has a saw-edged cross-section and is provided with anacute angled peak.

The press-fit portion 218 is force-fitted within the resin tube 200 andthereby the connector body 208 is connected to such resin tube 200.

At that time, the annular ribs 220 formed on the outer peripheralsurface of the press-fit portion 218 bite in an inner surface of an endportion of the resin tube 200 that is diametrically expanded anddeformed by force-fitting of the press-fit portion 218, and thereby theresin tube 200 is retained and stopped for preventing withdrawal.

Meanwhile, the press-fit portion 218 is formed with an annular groovewherein an O-ring 222 is retained. The O-ring 222 provides an air-tightseal between the press-fit portion 218 and the resin tube 200.

The above retainer holding portion 216 is a portion for holding theretainer 210 while receiving the retainer 210 therein. The connectorbody 208 is connected to the mating pipe 202 via the retainer 210.

The retainer holding portion 216 is provided with a stop portion(body-side stop portion) 224 on a trailing end (proximal end or axiallyouter end) thereof for latching onto the retainer 210.

On the other hand, the retainer 210 is a resin member that is as a wholegenerally annular, and resiliently or flexibly deformable in a radialdirection.

The retainer 210 is formed with an engaging recessed portion or engagingslit portion (retainer-side engaging portion) 225 and a latching recess(retainer-side latching portion) 226. The engaging projection 204 of themating pipe 202 engages with the engaging recessed portion 225 fromradially inward or inside the retainer 210. The latching recess 226similarly fits to the stop portion 224 of the connector body 208 fromradially inward or inside the retainer holding portion 216 to stop theretainer 210 in an axial direction.

The retainer 210 is held by the retainer holding portion 216 in anaxially fixed state by latching the latching recess 226 onto the stopportion 224 of the retainer holding portion 216.

The retainer 210 further includes an inner peripheral surface thereofthat defines a tapered inner peripheral cam surface 228, and an outerperipheral surface that defines a tapered outer peripheral cam surface230.

When the mating pipe 202 is inserted inside the retainer 210 in an axialdirection, the inner peripheral cam surface 228 abuts and guides theengaging projection 204 for further axial movement. Then the innerperipheral cam surface 228 resiliently diametrically expands theretainer 210 as a whole by the cam action as the engaging projection 204moves and thereby allows passage of the engaging projection 204.

Then, as soon as the engaging projection 204 reaches a position of theengaging recessed portion 225, the retainer 210 as a whole returns toits original shape, the engaging projection 204 simultaneously is fittedor slipped in the engaging recessed portion 225 in fixed relation withone another in an axial direction.

On the other hand, when the retainer 210 is inserted in the retainerholding portion 216 of the connector body 208 in the axial direction,the outer peripheral cam surface 230 abuts the stop portion 224, therebyresiliently diametrically contracts the retainer 210 as a whole, andlatches the latching recess 226 onto the stop portion 224 withdiametrically contracting action of the retainer 210.

Meanwhile, the retainer 210 is provided with operation tabs 231 ontrailing end portions (proximal end portions or axially outer ends, leftend portions in the figure) thereof. The retainer 210 also may bediametrically contracted by exerting a radially inward force to theoperation tabs 231.

In the connector 206, the retainer 210 is first held in the retainerholding portion 216 of the connector body 208. Then, in this state, themating pipe 202 is inserted inside the retainer 210 in the axialdirection.

During that time, the retainer 210 is resiliently expanded in adiametrically expanding direction by the engaging projection 204 of themating pipe 202. As soon as the engaging projection 204 reaches theengaging recessed portion 225, the retainer 210 diametrically contractsand the engaging projection 204 engages in the engaging recessed portion225.

On the other hand, the retainer 210 may be first attached to the matingpipe 202. Then, in this state, the mating pipe 202 with the retainer 210thereon may be inserted in the connector body 208.

During that time, the retainer 210 diametrically contracts once, then,as soon as the latching recess 226 reaches a position of the stopportion 224, the retainer 210 diametrically enlarges to latch thelatching recess 226 onto the stop portion 224.

The bush 214 and the O-rings 212 as sealing member are placed andretained in a distal end of the connector body 208 relative to theretainer holding portion 216. When the mating pipe 202 is insertedwithin the connector body 208, the O-rings 212 or the O-rings 212 andthe bush 214 contact air-tightly with an inserting end portion 232 ofthe mating pipe 202, namely an outer peripheral surface of a leading end(axially inner end) of the inserting end portion 232 relative to theengaging projection 204 (an outer peripheral surface of a leading endportion of the inserting end portion 232 extending from the engagingprojection 204), and provide an air-tight seal between the mating pipe202 and the connector body 208.

As shown in FIG. 12 (A), two O-rings 212 are used in the connector 206.However, as shown in FIG. 12 (B), as the case may be, single O-ring 212may be used in the connector 206 for compact sizing of the connector206.

As understood from the above, the resin tube 200 may be easily connectedwith the mating pipe 202 by use of such connector 206 with a simpleaction.

By the way, such connector as described in Patent Document 2 may be usedto be attached to an end portion of the resin tube 200. This connector300 is, as shown in FIGS. 14 and 15, configured such that a relativelythin-walled retainer 302 is mounted on a retainer holding portion 304 ina direction perpendicular to an axis.

The connector 300 has a connector body (here, entirely made of resin)306 in the form of a tubular shape as a whole, a retainer 302, O-rings308 as sealing member and a bush 310 (refer to FIG. 14 (A)).

The connector body 306 includes a short cylindrical retainer holdingportion 304 on one end of the connector body 306 along an axialdirection and a connecting portion 312 on the other end thereof alongthe axial direction, for example, as connecting portion to the resintube 200.

The retainer 302 in the form of a looped shape is configured byconnecting a pair of engaging portions (retainer-side engaging portions,retainer-side latching portions) 314 integrally to V-shaped bodies 316at one and the other ends of the engaging portions 314, respectively(refer to FIG. 14 (B). The retainer 302 is inserted in the retainerholding portion 304 via an opening 318 of the retainer holding portion304 by narrowing a width of the retainer 302, and then the retainer 302is returned to its original width (namely its original shape) in theretainer holding portion 304. The retainer 302 is located therein withits original shape.

When a mating pipe 202 (in the form of slightly different shape from themating pipe 202 shown in FIG. 12) is inserted in the retainer 302, theengaging projection 204 of the mating pipe 202 abuts slant guidesurfaces or slant guide cam surfaces 320 of the engaging portions 314.Then the engaging projection 204 pushes the slant guide cam surfaces 320radially outwardly, and advances while widening the retainer 302. Assoon as the engaging projection 204 passes through the engaging portions314, the retainer 302 is slightly narrowed so that the engaging portions314 engages with the engaging projection 204 in an axial direction(refer to FIG. 15). Here, the engaging portions 314 enter cutoutportions (body-side stop portions) 322 of the retainer holding portions304 and engage with the retainer holding portion 304 in the axialdirection. In this manner, the mating pipe 202 and the retainer 302 orthe connector body 306 are securely fixed in the axial direction. And,the mating pipe 202 may be pulled out of the connector 300 by pressingpress portions 324 of the retainer 302 radially inwardly, and therebywidening a distance between the engaging portions 314. As shown in FIG.16, in some case, enclosing portions 326 are formed in the opening 318so as to rise radially outwardly in order not to allow the pressportions 324 to protrude outwardly.

Or, a connector as shown in Patent Document 3 may be also used. Thisconnector 400 is, as shown in FIGS. 17 and 18, configured such that aretainer 402 of a horse-shoe shape is mounted on a retainer holdingportion 404 in a direction perpendicular to an axis. The connector 400is provided further with a checker member 406 for verifying connectionto the mating pipe 202.

The connector 400 has a connector body (here, entirely made of resin)408 in the form of a cylindrical shape as a whole, a retainer 402,O-rings 410 as sealing member, a bush 412 and the checker member 406(refer to FIGS. 17 and 18(B)).

The connector body 408 includes a short tubular retainer holding portion404 on one end of the connector body 408 along an axial direction and aconnecting portion 414 on the other end thereof along the axialdirection, for example, as connecting portion to the resin tube 200.

The checker member 406 is shaped a box and includes a pair of resilientarms 416 and stop recesses 418 on end portions of the resilient arms416. The checker member 406 is installed on an outer periphery of theretainer holding portion 404 in a direction perpendicular to an axis andis located in the retainer holding portion 404 so as to engage the stoprecesses 418 with bottom surface portions 420, respectively.

The retainer 402 includes a pair of detecting lugs 422 and detectingdetents 424 on end portions (free end portions) of the detecting lugs422, and the detecting detents 424 protrude radially inwardly. Theretainer 402 is mounted on an outer periphery of the retainer holdingportion 404 in the direction perpendicular to the axis and is located inthe retainer holding portion 404 so as to protrude the detecting detents424 inside a passage of the engaging projection 204 of the mating pipe202 (refer to FIG. 18 (A)).

When the mating pipe 202 is inserted in the connector body 408, theengaging projection 204 advances with pushing away slant guide surfacesor slant guide cam surface 425 and abuts the bush 412 (namely, themating pipe 202 is correctly connected to the connector body 408), thedetecting detents 424 of the retainer 402 are pushed and moved radiallyoutwardly by the engaging projection 204, engagement of the detectingdetents 424 and dents 430 of receiving slots 428 is cancelled, andthereby the retainer 402 is allowed to be further pushed in thedirection perpendicular to the axis. When the retainer 402 is furtherpushed in the direction perpendicular to the axis, engaging portions(retainer-side engaging portions) 431 of the retainer 402 engage withthe engaging projection 204 of the mating pipe 202, and simultaneously,the resilient arms 416 of the checker member 406 are moved by guide lugs432 of the retainer 402, the stop recesses 418 of the resilient arms 416are pushed radially outwardly, and thereby engagement of the stoprecesses 418 and the bottom surface portions 420 is cancelled. In thismanner, the mating pipe 202 and the connector body 408 are securelyfixed together in the axial direction. In this securely fixed relation,the checker member 406 is allowed to separate from the connector body408. That is, only when the mating pipe 202 is connected to theconnector 400 correctly, the checker member 406 can be removed from theconnector body 408. Meanwhile, the retainer 402 engages with restrainingflanges 434, 436, 438 (body-side stop portions) of the connector body404 at a rear end surface, middle recessed portions and a front endsurface (retainer-side stop portions) of the retainer 402 in an axialdirection.

The conventional resin tube 200 here is, for example, about 6 mm in aninner diameter and about 8 mm in an outer diameter, and adapted in apiping system as shown in FIG. 19.

In this piping system, a fuel in a fuel tank 234 is transported(supplied) by a fuel pump 236 through a supply channel 238 under acertain pressure, and injected from an injector 240 to a cylinder 242 ofan engine. And, a surplus fuel is returned through a return channel 244to the fuel tank 234. Preferably the piping and the resin tube as aboveis light-weight and has a small diameter in view of designing the pipingsystem and cost-reduction.

Meanwhile, a resin tube for transporting a fuel, for example, the resintube equipped with a connector is usually assembled in a motor vehiclebody according to a predetermined piping layout. Conventionally, theresin tube is formed or molded as a whole initially in a required bentor curved shape (initially bent or curved resin tube) according to thepredetermined piping layout in a formation or molding step of the resintube. Then the initially bent or curved resin tube is delivered to anassembling site and assembled in the motor vehicle body on theassembling site.

However, the bent or curved resin tube that is formed or moldedinitially in the bent or curved shape is obtained, for example, in thefollowing steps. A straight tubular resin tube is fitted in aconstraining mold to is retain the resin tube in a bent or curved shape,and the resin tube as a whole or the constraining mold is put into anoven to be heated, for example, at a temperature of 150° C. to 160° C.for 20 to 30 minutes to be formed into a bent or curved shape, then theconstraining mold is taken out from the oven, cooled, and the resin tubeis removed out of the mold (for example, as disclosed in Patent Document4 below). However, many production steps are required or exist in thisproduction method, resulting in increase of the production cost. And,here, the resin tube corresponding to the type of a motor vehicle,strictly speaking, corresponding to the type of the piping layout isrequired, and varied types of the resin tubes should be producedaccordingly. This is also a factor of the cost increase.

In the conventional structure for assembling a resin tube fortransporting a fuel, the resin tube is initially formed or molded in arequired bent or curved shape, and, for example, connected with themating pipes on both ends of the resin tube by means of connectors.However, this causes the following problem besides the above problems.

When vibration is transmitted from a motor vehicle body through themating pipe to the resin tube that is connected with the mating pipe viathe connector, the resin tube relatively rotates relative to the matingpipe, together with the connector, and thereby the sealing member suchas O-ring that is retained within the connector is worn and collapsed.As a result, such problem is caused that a sealing property is lowered.

Means for solving this problem are proposed in Patent Document 5 below.However, in this case, there still exists a problem that a particular,special connector and fixing clamp are required.

The problem as above notably occurs specifically in a vehicle wherein anengine is connected to a rear wheel so as to fluctuate along with therear wheel, namely the vehicle wherein when the rear wheel oscillates orvibrates and fluctuate relative to a motor vehicle body or the frame,the engine also fluctuates relative to the motor vehicle body or theframe, following the rear wheel.

In a two-wheeled motor vehicle wherein an engine and a fuel tank are isarranged and fixed on the same frame, a resin tube equipped with aconnector for transporting a fuel to the engine does not oscillatelargely, and therefore, the above problem is not so notable. However,particularly in a two-wheeled motor vehicle where an engine fluctuatesalong with a rear wheel (for example, disclosed in Patent Documents 6and 7 below), the above problem tends to be caused as a resin tubeequipped with a connector is subject to increased oscillation and theresin tube oscillates largely.

[Patent Document 1]JP-A, 11-201355

[Patent Document 2]JP-B, 2641683

[Patent Document 3]JP-A, 2004-251319

[Patent Document 4]JP-A, 6-190913

[Patent Document 5]JP-A, 9-269088

[Patent Document 6]JP-Y, 7-55192

[Patent Document 7]JP-Y, 7-46617

SUMMARY OF THE INVENTION

Under the circumstances described above, it is an object of the presentinvention to provide a novel piping structure for transporting a fuelwhere a resin tube, which is produced in decreased number of steps atlow cost, is used. In the piping structure, for example, the resin tubeassembled in a vehicle body is stably held against vibration transmittedfrom the motor vehicle body. It is another object of the presentinvention to provide a novel resin tube that is adapted in the novelpiping structure. And, it is yet another object of the present inventionto provide a novel method for producing the novel resin tube that isadapted in the novel piping structure.

According to the present invention, there is provided a novel pipingstructure for transporting a fuel that is arranged between an engine anda fuel tank, or a novel structure for assembling a resin tube in a motorvehicle body. The resin tube is arranged between the engine and the fueltank for transporting a fuel, and, for example, is equipped with aconnector. The piping structure for transporting a fuel or the structurefor assembling a resin tube comprises a resin tube for transporting afuel that is formed in a straight tubular shape and a fixing clamp forfastening the resin tube to a motor vehicle body or fixing the resintube in the motor vehicle body, and thereby assembling the resin tube inthe motor vehicle body. The resin tube is flexed and bent or curvedunder flexibility of the resin tube at one or more points along alongitudinal direction of the resin tube, to define a bent portion orone or more bent portions and thereby the resin tube is provided with apredetermined bent shape, for example, as a whole. That is, the resintube is in a form of a predetermined bent shape by bending and deformingthe resin tube that is formed in the straight tubular shape under itsflexibility. The fixing clamp securely fixes the resin tube or the bentportion in a motor vehicle body so as to retain the bent portion of theresin tube by clamping the resin tube or the bent portion. Here, as itis not necessary to form the resin tube in the predetermined bent shapeat a production step of the resin tube, a cost required for the resintube may be lowered. And, for example, the resin tube is in a form of astraight tubular shape until assembled in the motor vehicle body in anassembling step. The resin tube is provided with a predetermined bentshape, for example, a permanent predetermined bent shape and assembledin the motor vehicle in the step of assembling in the motor vehiclebody. So, it is not necessary to prepare specific type of a resin tubefor every different type of motor vehicle or for every different pipinglayout. It is advantageous that a common or same type of a resin tubemay be used widely for various types of motor vehicles or various pipinglayouts.

To an end portion of the resin tube, a connector is attached forconnecting the resin tube with a mating pipe, for example, before theresin tube is fastened to or fixed in the motor vehicle body. In thiscase, the resin tube is assembled in the motor vehicle body while beingconnected with the mating pipe via the connector or by means of theconnector. For example, a relative rotational movement of the connectorand the mating pipe is restrained by restraining action of the fixingclamp relative to the resin tube.

The fixing clamp may be arranged so as to retain the bent portion of theresin tube by fixing a region of each side of the bent portion of theresin tube in the motor vehicle body. This configuration allows toretain stably the resin tube in a form of bent shape. For example, theregions of both sides of the bent portion are clamped by the fixingclamps, respectively. And, as the regions of the both sides of the bentportion is securely fixed in the motor vehicle body, when vibration fromthe motor vehicle body is exerted to the resin tube, oscillation orvibration of the resin tube may be restrained small. Further, clampingor restraining action is also given to the resin tube by the fixingclamp, and thereby the resin tube itself does not rotate. So, forexample, the connector does not relatively rotate relative to the matingpipe or, the resin tube does not relatively rotate along with theconnector relative to the mating pipe. This may simultaneously solve theproblem that the sealing member such as O-ring in the connector is wornand collapsed due to relative rotational movement of the resin tuberelative to the mating pipe or relative rotational movement of the resintube relative to the mating pipe along with the connector and therebysealing property is lowered. So, good sealing property between theconnector and the mating pipe may be maintained for a long time.

The fixing clamp may be a metal clamp.

The resin tube or the resin tube equipped with a connector that isadapted in the present invention is in a form of a straight tubularshape in a forming or molding step, and is provided with a predeterminedbent shape when assembled in the motor vehicle body. This may lower theproduction cost.

Meanwhile, instead of a piping system (so-called a return fuel system)shown in FIG. 19, where a surplus fuel is returned to the fuel tank,another piping system, so-called retunless fuel system where a surplusfuel is not supplied but only a required quantity of the fuel, namely aquantity to be consumed is supplied from the fuel tank to the engine,has been increasingly applied recent years. In the returnless fuelsystem, only the required quantity of the fuel is supplied. Therefore,if the resin tube with the same diameter as in the piping system shownin FIG. 19 is used in the returnless fuel system, the fuel is likelyaccumulated. And, the fuel in accumulated state is evaporated in thepiping under a certain atmosphere in the engine room, and resultantly,the engine revolutions are liable to be unstable. In this case, for theresin tube, a small-diameter resin tube, for example, of an outerdiameter up to 6 mm (more preferably, up to 5 mm) is preferably used inorder not to cause accumulation of the fuel. For so-called compactvehicle with a small engine such as a mini-vehicle, specifically, atwo-wheeled motor vehicle, a three-wheeled motor vehicle, andall-terrain vehicle (ATV), it is preferable to use such small diameterresin tube or a small diameter resin tube with an inner diameter up to 4mm, for example, a small diameter resin tube with an inner diameter upto 3.5 mm in order to prevent the fuel from being accumulated. Further,it is more preferable to use a small diameter resin tube with an innerdiameter up to 3 mm, for example, a small diameter resin tube with aninner diameter up to 2.5 mm. Typically, the small diameter resin tubehas high flexibility compared to a large diameter resin tube.Specifically, such small diameter resin tube is excellent inflexibility. Therefore, when such small diameter resin tube is bent orcurved in the assembling step, the small diameter resin tube is hard tobe broken (kinked). And, it is possible to assemble such small diameterresin tube in the motor vehicle body by bending and curving the smalldiameter resin tube in a predetermined bent shape without difficulty.Further, the small diameter resin tube is favorable in view of designingof piping system and low production cost.

The piping structure for transporting a fuel or the structure forassembling a resin tube according to the present invention may bepreferably adapted in that the resin tube is connected via the connectorwith the mating pipe that is integrally formed in a component securelyfixed in the motor vehicle body. Such mating pipe fixed in the motorvehicle body entails a problem that the resin tube easily relativelyrotates relative to the mating pipe along with the connector due tooscillation of the motor vehicle body. However, according to the presentinvention, such relative rotation is effectively prevented and goodsealing property may be maintained. And, the piping structure fortransporting a fuel according to the present invention may be adaptedfor assembling of the resin tube in a motor vehicle wherein an engine isconnected to or connected integrally to a rear wheel so as to fluctuatealong with the rear wheel or so as to fluctuate integrally with the rearwheel, and in this case, the resin tube may be effectively preventedfrom oscillation or rotational movement.

The fixing clamp may be constructed to have a generally annular holdingportion, and to have an opening through which the resin tube is fittedin the holding portion in a direction perpendicular to an axis, forexample, before the resin tube is clamped. The fixing clamp isconstructed such that the opening is closed when the fixing clamp isfixed in the motor vehicle body while holding the resin tube in theholding portion in order to assemble the resin tube in the motor vehiclebody. The fixing clamp with such construction allows an operator to fixthe resin tube in the motor vehicle body easily by means of the fixingclamp while bending the resin tube in an assembling site. At the sametime, as the opening has been closed after the resin tube is fixed inthe motor vehicle body by the fixing clamp, even if a great oscillatingforce acts on the resin tube, the resin tube and the fixing clamp arerestrained from relative movement, and thereby a defect such as rubbingof the resin tube and the fixing clamp may be avoided.

The connector that is used here may have, a) a connector body, includinga retainer holding portion on one end of the connector body along anaxial direction and a connecting portion on the other end of theconnector body for being connected to the resin tube, for example, in aform of a cylindrical shape as a whole, b) a retainer held in or on theretainer holding portion, for example, for engaging with a pipe sideengaging portion in a form of a projection or recess on an outerperipheral surface of the mating pipe, and at a position spaced apartfrom an axial end of an inserting end portion of the mating pipe, and c)a sealing member placed, for example, inside the other end of theconnector body relative to the retainer holding portion. For example,the retainer securely fixes the mating pipe or the inserting end portionof the mating pipe that is inserted in the connector body in an axialdirection. The sealing member contacts with an outer peripheral surfaceof the mating pipe, or the inserting end portion of the mating pipe thatis inserted in the connector body to provide a seal relative to themating pipe or the inserting end portion thereof. And, the retainerholding portion may be configured in a form of a socket shape, and theconnecting portion may be configured as a fit-in portion to be forcefitted inside the resin tube. In this connector, the retainer is formedseparately from the connector body or unitary with the connector body,and designed resiliently or flexibly deformable in a radial direction.The retainer may have a retainer-side latching portion. The retainerside latching portion fits to or latches onto a body-side stop portionthat is formed on a side of retainer holding portion of a connector bodyfrom radially inward or inside the retainer holding portion to stop theretainer in the axial direction. The retainer further may have, at leastone of an inner peripheral cam surface and an outer peripheral camsurface. The inner peripheral cam surface resiliently diametricallyenlarges the retainer when the mating pipe is inserted in the retainer.On the other hand, the outer peripheral cam surface resilientlydiametrically contracts the retainer when the retainer is inserted inthe retainer holding portion.

Meanwhile, when the resin tube formed in a straight tubular shape isflexibly bent or deformed in a bent shape, and is assembled and securelyfixed in the motor vehicle body by the fixing clamp, there is a fearthat a scratch is created at a clamped part of the resin tube by thefixing clamp. And, when the resin tube has a scratch, there is anotherfear that deterioration of the resin tube progresses quickly. So, it isdemanded that such scratch is not created on the resin tube when theresin tube is clamped by the fixing clamp. And, as the resin tube formedin a straight tubular shape is bent or deformed in various bent shapesfor being assembled in the motor vehicle body, positioning of a part ofthe resin tube to be clamped or clamped by the fixing clamp is variedaccording to the bent shape of the resin tube. Accordingly, it is alsodemanded that no scratch is created on the resin tube whichever part ofthe resin tube is clamped by the fixing clamp.

According to the present invention there is also provided a novel resintube for transporting a fuel that is used in the piping structure fortransporting a fuel that is arranged between an engine and a fuel tank,or the structure for assembling a resin tube in a motor vehicle body.The resin tube is arranged between the engine and the fuel tank fortransporting a fuel, and, for example, is equipped with a connector. Theresin tube comprises a small diameter resin tube body with an outerdiameter up to 6 mm, and an elastic clamped layer laminated on an outerside or outer peripheral surface of the resin tube body to be clamped bythe fixing clamp. The elastic clamp layer has a predetermined wallthickness and covers the resin tube body along an entire effectivelength or entire effective portion of the resin tube that effectsflexing deformation.

Here, a highly flexible resin tube is formed or molded in a straighttubular shape that has an outer diameter, for example, up to 6 mm and issuitably adapted mainly for a compact vehicle with a small engine,specifically a two-wheeled motor vehicle. The resin tube in a form of astraight tubular shape is flexibly bent or deformed in a bent shape whenassembled in the motor vehicle body, and then assembled and securelyfixed by the fixing clamp in the motor vehicle body. In the presentinvention, an elastic clamped layer with a predetermined wall-thicknessis laminated on an outer side or an outer peripheral surface of theresin tube body along an entire effective length of the resin tube thateffects flexing deformation of the resin tube, for being clamped by thefixing clamp. So, this clamped layer laminated on the outer side or theouter peripheral surface of the resin tube body effectively preventscreating a scratch on the resin tube body when the resin tube is clampedby the fixing clamp.

And, as the clamped layer is provided along a substantially entirelength of the resin tube body, it may be effectively prevented to causea scratch on the resin tube or resin tube body also in case where theresin tube is clamped at any or discretional points thereof by thefixing clamp. Therefore, an operator can assemble the resin tube in themotor vehicle body in a good state.

That is, according to the present invention, an operator can clamp bythe fixing clamp any points of the resin tube along a longitudinaldirection thereof without creating a scratch on the resin tube body,thereby can provide the resin tube with various bent shapes as desired,and assemble and pipe the resin tube.

Meanwhile, in an ordinary four-wheel motor vehicle, conventionally, asthe case may be, a resin tube is covered with a protector made of rubberon an outer peripheral surface thereof.

However, in this case, the protector is provided for the purpose forprotecting the resin tube from flying pebbles, and protecting ordelaying the resin tube from melting in case of fire, etc. or the like.

It is not specifically demanded to provide the protector on the resintube for transporting a fuel in a compact vehicle with a small engine,specifically two-wheeled motor vehicle wherein a small diameter tubewith an outer diameter up to 6 mm is used.

In the present invention, the clamped layer of the resin tube isprovided not for the purpose of protecting the resin tube from flyingpebbles or fire, but resolutely for the purpose of protecting the resintube from adverse affects by being clamped by the fixing clamp.Therefore, a wall-thickness of the clamped layer is decided according tothis purpose.

For that purpose, in the present invention, the clamped layer preferablyhas a wall-thickness in a range of 0.7 to 1.3 mm. In the resin tube withthe clamped layer of a wall thickness under 0.7 mm, it becomes difficultto protect sufficiently the resin tube body from suffering a scratchwhen the resin tube is clamped by the fixing clamp. In view ofprotecting the resin tube body from suffering a scratch, it issufficient to form the clamped layer with a wall-thickness of 1.3 mm. Onthe contrary, in the resin tube with the clamped layer of a wallthickness above 1.3 mm, there is a fear that a problem is posed inflexing deformation of the resin tube into bent shape or fixing of theresin tube by the fixing clamp, etc., during assembling of the resintube in the motor vehicle body.

By the way, when such clamped layer is provided so as to cover the resintube along an entire length of the resin tube, specifically from one endto the other end of the tube body, a following problem arises.

When the resin tube is connected with the mating pipe via the connector,the resin tube is connected to the connector prior to assembling theresin tube in the motor vehicle body. The connector may include atubular nipple portion as a force-fit portion to be force fitted in theresin tube, and the nipple portion is provided with an annular sealingmember such as O-ring fitted on the outer peripheral surface thereof.

At that time, an end portion of the resin tube body is expanded in aflared shape (flared out) in order to force fit the nipple portiontherein. However, the clamped layer, which covers the resin tube body toextreme ends of the resin tube body, overlies an end surface of a flaredportion after the end portion of the resin tube body is flared out. And,when the nipple portion of the connector is force fitted inside theresin tube, a part of the clamped layer overlying the end surface of theflared portion could damage the sealing member such as the O-ring fittedon an outer peripheral surface of the nipple portion. Or the nippleportion could be force fitted inside the resin tube such that the partof the clamped layer overlying the end surface is caught in or jammed bythe sealing member. As a result, there arises a fear that the sealingproperty between the nipple portion of the connector and the resin tubeis lowered.

Therefore, preferably, the clamped layer is removed for a predeterminedlength from an extremity or opposite extremities of the resin tube bodyso as to expose an end portion or opposite end portions of the resintube body. This configuration may solve the above-mentioned problem.That is, the clamped layer does not overlie the end surface of theflared portion when the end portion of the resin tube body is flaredout. And, when the nipple portion of the connector is force fittedinside the resin tube, the sealing member such as O-ring fitted on theouter peripheral surface of the nipple portion is not damaged, and theend of the clamped layer is not caught in by the sealing member. As aresult, solved is the problem that the sealing property is lowered.

In this configuration, the clamped layer is preferably removed forlength of 2 to 8 mm from an extreme end (the extremity) or oppositeextreme ends (the opposite extremities) of the resin tube body. That is,an end portion or opposite end portions of the clamped layer are removedfor a length of 2 to 8 mm from the extremity or the opposite extremitiesof the resin tube body.

In the resin tube here, the clamped layer is first laminated or formedon the resin tube body so as to cover an entire length from one end tothe other end thereof. Then, a generally cylindrical cutting guard isslid from a longitudinal end or each longitudinal end of the resin tubebody and the clamped layer, namely from a longitudinal extremity or eachlongitudinal extremity thereof, between the resin tube body and theclamped layer, to protect or guard the resin tube body. And, the clampedlayer is cut annularly near extreme end thereof or each extreme endthereof and an annular end portion or each of annular end portions ofthe clamped layer is removed from on the resin tube body by a cuttingblade while protecting the resin tube body from being cut by the cuttingguard. According to this production method of the present invention, anend portion or each end portion of the clamped layer may be removedfavorably from an outer peripheral surface of the resin tube body for apredetermined length without damaging the resin tube body.

Meanwhile, the resin tube is formed or molded in a straight tubularshape, and is fastened to or fixed in the motor vehicle body by thefixing clamp while being flexibly bent or deformed into a bent shape atassembling the resin tube in the motor vehicle body. In this case, theflexible resin tube tends to be kinked due to its flexibility. However,it is difficult for an operator to find that the resin tube is kinked,and there is a fear that the resin tube is assembled in the motorvehicle body by the operator while kinked.

In this case, there could be an obstacle in transporting a fuel. Orthere is caused a problem that kink of the resin tube causes a largestress in the resin tube and the resin tube tends to be deteriorated ata location of the stress generated.

Further, there is also a fear that due to the stress generated, themating pipe contacts partially with the sealing member such as O-ringthat is fitted in the connector, and thereby the sealing property islowered.

The above explanation is based on a typical instance of a small diametertube. However, such problems could arise commonly in a case where aresin tube is formed or molded in a straight tubular shape, and isfastened to or fixed in a motor vehicle body by the fixing clamp whilebeing flexibly bent or deformed in a bent shape in an assembling of theresin tube in the motor vehicle body.

It is required that the resin tube is prevented from being assembled inthe motor vehicle body while kinked, or the resin tube is not subject tounreasonable distortion that accelerates deterioration of the resintube. And it is also required that assembling of the resin tube does notresult in kink of the resin tube or partial contact between the matingpipe and the sealing member of the connector, and thereby in loweredsealing property. So, there is a demand for such resin tube to meet theforegoing requirements.

According to the present invention there is provided another novel resintube for transporting a fuel that is used in the piping structure fortransporting a fuel that is arranged between an engine and a fuel tank,or the structure for assembling a resin tube in a motor vehicle body.The resin tube is arranged between the engine and the fuel tank fortransporting a fuel, and, for example, is equipped with a connector. Theresin tube is provided with a mark on an outer peripheral surface of theresin tube, along a generally entire length or along an entire length ofthe resin tube. The mark extends linearly in a longitudinal direction ofthe resin tube in a state that the resin tube extends straight. Withthis resin tube with the mark thereon, when the resin tube is kinkedduring assembling in the motor vehicle body, a kink is produced in themark arranged linearly as well as in the resin tube itself, and anoperator can easily and visually verify by the mark that a kink isproduced in the resin tube.

So, the operator can arrange and assemble the resin tube withoutproducing a kink in the resin tube by maintaining a linear arrangementof the mark on the resin tube.

This configuration produces a major effect when adapted specifically toa small diameter resin tube with an outer diameter up to 6 mm, and to aresin tube that is to be connected with the mating pipe via a connectorwhich is rotatable relative to the mating pipe and includes an annularsealing member such as an O-ring to provide a seal relative to themating pipe.

More specifically, in case where a connector is attached to an endportion of a resin tube for connecting the resin tube with the matingpipe, and the connector is provided with a checker member for verifyingcomplete connection with the mating pipe, for example, the mark isprovided on the resin tube so as to correspond to, conforming to orgenerally conform to a mounting and removing direction of the checkermember, or the mounting and removing side of the checker member relativeto a circumferential position. Or, the mark may be provided on the resintube so as to correspond to, conform to, or generally conform to adiametrically opposite side to the mounting and removing direction ofthe checker member or the mounting and removing side of the checkermember relative to a circumferential position.

Or, in case where a connector is attached to an end portion of a resintube for connecting the resin tube with the meting pipe, and theconnector is provided with a retainer for engaging with the mating pipe,the retainer has an operating portion that does not project radiallyfrom the connector, the operating portion is configured so as to cancelengagement of the mating pipe with the connector or with the retainer bybeing operated, for example, the mark is provided on the resin tube soas to correspond to, conform to or generally conform to the operatingportion or an operating direction of the operating portion relative to acircumferential position.

Now, the preferred embodiments wherein the present invention is adaptedfor an assembling structure of a resin tube equipped with a connector tobe arranged between an engine and a fuel tank in a compact vehicle fortransporting a fuel will be described in detail with reference to thedrawings.

Here, the compact vehicle means specifically a two-wheeled motorvehicle, a three-wheeled motor vehicle, and all-terrain vehicle (ATV) orthe like, or a mini-vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (A) is a view showing a piping structure for transporting a fuelaccording to one embodiment of the present invention.

FIG. 1 (B) is an enlarged view of a part B of FIG. 1 (A).

FIG. 1 (C) is another enlarged view of the part B of FIG. 1 (A).

Fig. 2 (A) is a partly exploded sectional view of a connector of the oneembodiment.

Fig. 2 (B) is a sectional view showing a state that a resin tube isconnected with a mating pipe by means of the connector.

FIG. 3 is a partly exploded perspective view showing the connector alongwith a mating pipe.

FIG. 4 (A) is a front view showing the resin tube equipped with theconnector of the one embodiment, before assembled in a motor vehicle.

FIG. 4 (B) is a sectional view taken along B-B line of FIG. 4 (A).

FIG. 4 (C) is an enlarged view of a part C of FIG. 4 (A).

FIG. 4 (D) is a view showing an example of providing the resin tube witha mark.

FIG. 5 is a view showing a fixing clamp according to the one embodimentof the present invention, before fastened.

FIG. 6 (A) is a perspective view showing a state that the resin tube isfastened by the fixing clamp.

FIG. 6 (B) is a sectional view showing that the resin tube is fastenedby the fixing clamp.

FIG. 7 (A) is a front view showing another mode of a fixing clamp.

FIG. 7 (B) is a sectional view showing the another mode of the fixingclamp.

FIG. 7 (C) is a sectional view of a buffer member that is used in theanother mode of the fixing clamp.

FIG. 7 (D) is another sectional view of the buffer member.

FIG. 8 (A) is a perspective view showing a state that the resin tube isfastened by the another mode of the fixing clamp.

FIG. 8 (B) is a sectional view showing a state that the resin tube isfastened by the another mode of the fixing clamp.

FIG. 8 (C) is a view showing a piping structure where the another modeof the fixing clamp is used.

FIG. 8 (D) is an enlarged view showing a part D of FIG. 8 (C).

FIG. 9 is a view showing yet another mode of a fixing clamp.

FIG. 10 (A) is a view showing a first step of a production process ofthe resin tube of the one embodiment.

FIG. 10 (B) is a view showing a second step of the production process ofthe resin tube of the one embodiment.

FIG. 10 (C) is a view showing a third step of the production process ofthe resin tube of the one embodiment.

FIG. 10 (D) is a view showing a fourth step of the production process ofthe resin tube of the one embodiment.

FIG. 10 (E) is a view showing a fifth step of the production process ofthe resin tube of the one embodiment.

FIG. 11 (A) is a view showing a first step of a production method by wayof comparison to the production process shown in FIG. 10.

FIG. 11 (B) is a view showing a second step of the production method byway of comparison to the production process shown in FIG. 10.

FIG. 11 (C) is a view showing a third step of the production method byway of comparison to the production process shown in FIG. 10.

FIG. 12 (A) is an example of a conventional piping structure.

FIG. 12 (B) is a view of a connector shown in FIG. 12 (A), where exactone O-ring is used.

FIG. 13 (A) is a view of a relevant part of the connector of FIG. 12along with a resin tube, and showing a state before the connector isforce-fitted in the resin tube.

FIG. 13 (B) is a view of the relevant part of the connector of FIG. 12along with the resin tube, and showing a state that the connector isforce-fitted in the resin tube.

FIG. 14 (A) is a sectional view of another connector.

FIG. 14 (B) is a view showing a retainer of the another connector.

FIG. 15 is a sectional view showing a state that the another connectoris connected to the mating pipe.

FIG. 16 is a view showing a modified example of the another connector.

FIG. 17 is an exploded perspective view of yet another connector.

FIG. 18 (A) is a sectional view of the yet another connector.

FIG. 18 (B) is a view showing that the yet another connector isconnected to the mating pipe.

FIG. 19 is a schematic view of a return fuel system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 2 and 3, reference numeral 10 is a mating pipethat is formed integrally to a component such as an engine or a fueltank securely fixed to a motor vehicle body. The mating pipe 10 isformed with an engaging projection (pipe-side engaging portion) 12projecting annularly on and around an outer peripheral surface thereof.

FIG. 4 shows a resin tube equipped with a connector to be arrangedbetween an engine and a fuel tank in a state before assembled in themotor vehicle body. In Figures, reference numeral 14 indicates the resintube, reference numeral 16 indicates the connector (quick connector).The connectors 16, 16 are attached to both end portions of the resintube 14. However, when the resin tube 14 is connected directly to amating member such as the mating pipe 10 on one end portion of the resintube by force-fitting or the like, the connector 16 is attached only tothe other end portion of the resin tube 14.

Here, the resin tube 14 has a straight tubular shape before assembled inor to the motor vehicle body. That is, the resin tube 14 is formed ormolded in the straight tubular shape.

Meanwhile, the resin tube 14 equipped with the connector 16 is adaptablefor a returnless fuel system where a surplus fuel is not returned to thefuel tank and for another fuel system where a surplus gasoline isreturned to the fuel tank (return fuel system).

As shown in FIG. 4 (B), reference numeral 14A is a resin tube body ofthe resin tube 14. The resin tube body 14A has a multilayeredconstruction that includes an inner layer 14A-1 made of ETFE and anouter layer 14A-2 made of PA 12.

Further, a clamped layer or to-be-clamped layer 14B is laminated on anouter peripheral surface of the resin tube body 14A so as to cover theresin tube body 14A along an entire effective length thereof thateffects flexing deformation, specifically, along an entire length of thetube body 14A except for the both end portions of the resin tube body14A. The effective length is indicated by L′, shorter than an entirelength L of the resin tube 14. The effective length L′ is, for example,a length of the resin tube 14 except for both end portions in which anipple portion 28 (to be described later) of the connectors 16 arefitted. Here, the clamped layer 14B is formed slightly longer than theeffective length L′. That is, in this embodiment, the clamped layer 14Bis also laminated on a part or inner part of a region of the resin tubebody 14A in which the nipple portion 28 of the connector 16 is forcefitted, namely, the part or inner part of the region of the resin tubebody 14A that is fitted on the nipple portion 28.

Concretely, the resin tube body 14A is entirely covered with the clampedlayer 14B except at regions extending for a distance δ from bothextremities of the resin tube body 14A in axially inward direction. Inthis embodiment, the distance δ is equal to 2 to 8 mm.

Here, the clamped layer 14B is provided for being clamped by a fixingclamp which will be described later.

In this embodiment, the resin tube body 14A is a small diameter tubethat has an inner diameter (id) of 2.5 mm, an outer diameter (od) of 4mm. Namely, the inner layer 14A-1 has an inner diameter (id) of 2.5 mm,and the outer layer 14A-2 has an outer diameter (od) of 4 mm.

Here, the inner layer 14A-1 has a wall thickness of 0.2 mm, the outerlayer 14A-2 has a wall thickness of 0.55 mm, and the clamped layer 14Bhas a wall thickness of 1.0 mm. That is, wall thickness (t) of the innerlayer 14A-1 and the outer layer 14A-2, namely a wall thickness (t) ofthe resin tube body 14A is 0.75 mm.

The resin tube 14 is designed to have the entire length-L of 200 to 1500mm.

However, the multilayered construction, material and dimension such aswall thickness and length are given by way of example. Needless to say,these may be modified variously.

As shown in FIG. 2, the connector 16 has a connector body (here,entirely made of resin) 18 of a tubular shape as a whole, a retainer 20,a bush 24 and O-rings 22, 22 as sealing member (also refer to FIG. 3).For example, the O-ring 22 functions as sealing member, while the bush24 functions not as sealing member but as stop against lateral wobblingwith respect to an axis.

In this embodiment, the connector 16 is made of PA (except the sealingmember). However, the material for the connector 16 is selectablesuitably in view of heat resistance, fuel impermeablity, gasolineresistance (resistance to swelling in gasoline) and cost.

Specifically, polyamide type (PA11, PA12, P6, PA66, polyphtalamide (PPA), etc.) and polyphenylene sulphide (PPS) or the like are excellentin heat resistance, and polyester type (polybutylene terephthalate(PBT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN),etc.) is excellent in fuel impermeability and resistance to gasoline.

And, polyacetal (POM) is available at relatively low cost while securingheat resistance, fuel impermeability, and resistance to gasoline.

And, glass fiber may be added in the above materials to enhance strengthor nanocomposite material such as clay may be added in the abovematerials to improve the fuel impermeability.

These materials are also suitable for a material for the resin tube body14A. For the material of the resin tube 14 or the resin tube body 14A,an alloy of elastomer and one of these resin materials may be used. Suchalloy may provide the resin tube 14 or the resin tube body 14A withflexibility in addition to heat resistance and fuel impermeabilityinherent in resin itself.

The above connector body 18 has a socket like retainer holding portion26 on an proximal end thereof and a press-fit or force-fit portion(nipple portion) 28 on a distal end thereof as a connecting portion tothe resin tube 14, as shown in FIG. 2.

The retainer holding portion 26 is a portion for receiving and holdingthe retainer 20 therein. The connector body 18 is connected to themating pipe 10 via the retainer 20.

The retainer holding portion 26 is formed with a pair of opening windows30, 30 and stop portions (body-side stop portions) 32, 32 on a trailingend thereof for being latched in the retainer 20. The pair of theopening windows 30, 30 are disposed in a diametrically symmetricalpositions with each other.

And, the retainer 20 is a member of generally annular shape (here,C-shape in section) as a whole and made of resin. The retainer 20 isdesigned resiliently and flexibly deformable in a radial direction.

The retainer 20 has engaging recessed portions or engaging slit portions(retainer-side engaging portions) 34, 34 and latching recesses(retainer-side latching portions) 36, 36. The engaging projection 12 ofthe mating pipe 10 engages with the engaging recessed portion(retainer-side engaging portion) 34 from radially inward or inside theretainer 20 to be securely fixed in an axial direction, while thelatching recess 36 similarly fits to or latches onto the stop portion 32of the connector body 18 from radially inward or inside the retainerholding portion 26 to stop the retainer 20 in the axial direction.

The retainer 20 is held by the retainer holding portion 26 in fixedrelation in the axial direction while latching the latching recess 36onto the stop portion 32 of the retainer holding portion 26.

The retainer 20 further includes an inner peripheral surface thatdefines a tapered inner peripheral cam surface (a tapered innerperipheral guide surface or a tapered inner peripheral abutment surface)38, and an outer peripheral surface that defines a tapered outerperipheral cam surface (a tapered outer peripheral guide surface or atapered outer peripheral abutment surface) 40.

The inner peripheral cam surface 38 abuts the engaging projection 12,and guides the engaging projection 12 for axial movement when the matingpipe 10 is inserted inside the retainer 20 in the axial direction. Asthe engaging projection 12 moves, the inner peripheral cam surface 38resiliently diametrically enlarges the retainer 20, for example, as awhole under camming action or guiding action so as to allow passage ofthe engaging projection 12.

Then, as soon as the engaging projection 12 reaches a position of theengaging recessed portion 34, the retainer 20 returns to its originalshape as a whole, and simultaneously, the engaging projection 12 isfitted in the engaging recessed portions 34, 34 in fixed relation withone another in an axial direction.

On the other hand, when the retainer 20 is inserted in the retainerholding portion 26 of the connector body 18 in the axial direction, theouter peripheral cam surface 40 abuts the stop portions 32, 32, therebyresiliently diametrically contracts the retainer 20, for example, as awhole, and finally latches the latching recesses 36, 36 onto the stopportions 32, 32, respectively.

The retainer 20 includes operation tabs 42, 42 on trailing end portions(proximal end portions or axially outer ends) thereof. The retainer 20may also be diametrically contracted by exerting a force to theoperation tabs 42, 42 radially inwardly.

In the connector 16, the retainer 20 is first held in the retainerholding portion 26 of the connector body 18, and in this state, themating pipe 10 is inserted inside the retainer 20 in the axialdirection.

During that time, the retainer 20 is resiliently expanded in adiametrically expanding direction by the engaging projection 12 of themating pipe 10. And, as soon as the engaging projection 12 reaches theengaging recessed portions 34, 34, the retainer 20 diametricallycontracts and the engaging projection 12 engages in the engagingrecessed portion 34.

Alternatively, the retainer 20 is first attached to the mating pipe 10,and in this state, the mating pipe 10 with the retainer 20 thereon maybe inserted in the connector body 18.

At that time, the retainer 20 once diametrically contracts, and then, assoon as the latching recess 36 reaches a position of the stop portion32, the retainer 20 diametrically expands and the latching recess 36latches onto the stop portion 32.

The bush 24 and the above O-rings 22, 22 as the sealing member areequipped and held inside a distal end or leading end of the connectorbody 18 relative to the retainer holding portion 26. As soon as themating pipe 10 is inserted in the connector body 18, the O-rings 22, 22or the O-rings 22, 22 and the bush 24 contact air-tightly with aninserting end portion 44 of the mating pipe 10, namely an outerperipheral surface of a leading end of the inserting end portion 44relative to the engaging projection 12 (or an outer peripheral surfaceof a leading end of the mating pipe 10 extending from the engagingprojection 12 in a leading direction (traveling direction) of the matingpipe 10) to provide an air-tight seal between the mating pipe 10 and theconnector body 18.

The force-fit portion 28 is a portion to be force fitted or press fittedinside the resin tube 14 in the axial direction. The force-fit portion28 is formed with annular ribs 46 at a plurality of axially spacedpositions (here, two positions) on an outer peripheral surface thereof.The annular rib 46 has a saw-edged cross-section and is provided with anacute angled peak.

The connector body 18 is stopped relative to the resin tube 14 by forcefitting the force-fit portion 28 in an end of the resin tube 14.Meanwhile the connector body 18 may be stopped relative to the resintube 14 by other means than force fitting, for example, such as weldingand overmolding.

FIGS. 1 (A) and 1 (B) show a state that the above resin tube 14 equippedwith the connector 16 is assembled in a motor vehicle body.

As shown in the figures, here, the resin tube 14 is bent or curved inarcuate shape at a plurality of points (here, three bent points 50-1,50-2, 50-3) along a longitudinal direction based on its flexibility.Both side portions of each of the plurality of the bent points 50-1,50-2, 50-3 are held and fastened to the motor vehicle body by fixingclamps.

In this manner, the resin tube 14 equipped with connectors 16, 16 isentirely provided with bends or bent portions as predetermined. And theresin tube 14 in this state is assembled in the motor vehicle body whilebeing connected with the mating pipes 10 via the connectors 16, 16.

That is, the resin tube 14 that is formed in straight tubular shape isarranged and assembled in the motor vehicle body while being restrainedand retained in bent shape as desired by the fixing clamp.

Namely, the resin tube 14 formed in a straight tubular shape is arrangedand assembled in the motor vehicle body in a bent shape as desired underrestraining and constraining force by the fixing clamp.

FIGS. 5 and 6 show a preferred embodiment of the fixing clamp.

Here, FIG. 5 shows the fixing clamp 48 before fixed to the motor vehiclebody, while FIG. 6 shows the fixing clamp 48 after fixed thereto.Meanwhile, FIG. 1(A) shows the piping structure where the fixing clamp48 is used.

In FIG. 5, the fixing clamp 48 is made of resin, and is flexible orresilient. The fixing clamp 48 has a holding portion 54 and a mountingportion 56. The holding portion 54 is formed in generally annular shapeas a whole, and provided with an opening 52 in a predeterminedcircumferential position thereof. The holding portion 54 includes a pairof guide duck bill portions 53, 53 projecting outwardly, on both ends ofthe opening 52. Thereby the holding portion 54 is in a form of generallyC-shape. The mounting portion 56 has an insert portion 59 for a holdingbore 57 in a panel of a side of the motor vehicle body, and a pair ofpinching portions 61A, 61B for pinching the panel from inside andoutside the panel. The pinching portion 61A is formed integrally on anouter end portion of the mounting portion 56 or the insert portion 59(an end portion of the mounting portion 56 or the insert portion 59 nearthe holding portion 54) so as to extend in both lateral directions (bothlaterally outward directions, in right and left directions in FIG. 5),while the pinching portion 61B is formed integrally on an inner endportion of the mounting portion 56 or the insert portion 59 (an endportion of the mounting portion 56 or the insert portion 59 opposite tothe holding portion 54) so as to extend in the both lateral directions.The pinching portion 61-B integrally includes foot portion 61B-1 thatextends laterally outwardly and is angled toward the holding portion 54on both lateral sides, and turned-back portion 61B-2 that extends inlaterally inward direction from laterally outer ends of the foot portion61-B and is angled toward the holding portion 54. A distance betweenlaterally outer ends of the pinching portion 61A is sufficiently greaterthan a width of the holding bore 57, and a distance between laterallyouter ends of the pinching portion 61B (a distance between laterallyouter ends of the foot portion 61B-1) is slightly greater than the widthof the holding bore 57.

As shown in FIG. 6 (A), in the fixing clamp 48, the resin tube 14 isslipped in the holding portion 54 via the opening 52 in a directionperpendicular to an axis while resiliently widening the holding portion54, and thereby the resin tube 14 is held by the holding portion 54.Then the fixing clamp 48 is securely fixed to the motor vehicle body inthe holding bore 57, and thereby the resin tube 14 is in fixed relationto the motor vehicle body. The fixing clamp 48 is securely fixedthereto, for example, in a following manner. The insert portion 59 isinserted in the holding bore 57 of the panel such that the pinchingportion 61B is force-fitted within the holding bore 57, for example,while being narrowed or deformed laterally inwardly, and until thepinching portion 61B completely or generally completely passes throughthe holding bore 57 on to a rear side of the panel. In this mountedstate, laterally outer end portions of the pinching portion 61A engagewith a surface of the panel, while the turned-back portion 61B-2 of thepinching portion 61 B engages with an edge or an inner edge of theholding bore 57. Accordingly, for example, the fixing clamp 48 ismounted stably in the panel. On the other hand, it is carried outsmoothly to insert the fixing clamp 48 in the holding bore 57 and it ispossible to pull the fixing clamp 48 out of the holding bore 57.

FIGS. 7 and 8 show another preferred embodiment of a fixing clamp orfixing clamp device. Here, FIG. 7 shows the fixing clamp or fixing clampdevice before fixed in the motor vehicle body, while FIG. 8 shows thefixing clamp or fixing clamp device after fixed therein.

In FIG. 7, another fixing clamp 62 is made of metal, and has a holdingportion 63 in a form of generally annular shape as a whole and a pair ofmounting or fixing portions 64 in a form of plates that extend from bothcircumferential ends of the holding portion 63.

Each of the mounting portions 64 includes a mounting aperture 66. Themounting portions 64 are fastened to or securely fixed in the motorvehicle body by way of the mounting apertures 66. Here, in the statebefore clamped as shown in FIG. 7, the another fixing clamp 62 includesan opening 65 through which the resin tube 14 is fitted in the holdingportion 63 in a direction perpendicular to an axis.

Reference numeral 67 indicates a buffer member made of an elasticmaterial (here, made of rubber) that is interposed between the metalanother fixing clamp 62 and the resin tube 14. The buffer member 67includes a cylindrical portion 68, flange portions 69 on either endthereof, and a buffer member opening 70 in a predeterminedcircumferential position thereof.

That is, the buffer member 67 is in the form of C-shape as a whole.

In this fixing clamp device (the fixing clamp 62 and the buffer member67), as shown in FIG. 8, the cylindrical portion 68 of the buffer member67 is first fitted in the holding portion 63. In this sate, the resintube 14 is inserted in the buffer member 67 via the opening 65 and thebuffer member opening 70, and then, the another fixing clamp 62 isfastened to or securely fixed in the motor vehicle body at the mountingapertures 66. At that time, the another fixing clamp 62 securely fixesthe resin tube 14 in the motor vehicle body with the opening 65 closed(refer to FIG. 8 , FIG. 8 (C) and FIG. 8 (D) show a state that the resintube 14 is fastened to the motor vehicle body by the fixing clamp 62).Namely, the another fixing clamp 62 is securely fixed in the motorvehicle body such that the pair of mounting portions 64 are approachedor contact each other to be joined together.

Alternatively, the resin tube 14 may be first fitted in the buffermember 67, and in this state the resin tube 14 with the buffer member 67thereon may be inserted and held in the holding portion 63 of theanother fixing clamp 62 via the opening 65 in the directionperpendicular to the axis.

Although the buffer member 67 is applied here, the resin tube 14 may befitted directly in the another fixing clamp 62, and thereby the resintube 14 may be securely fixed in the motor vehicle body. By the way, inFIG. 8 (C), the resin tube 14 that is not provided with a mark 88 isused. However, the resin tube 14 may be provided with the mark 88, atthe front of the resin tube 14 in the figure, similarly to the one inFIG. 1 (A).

FIG. 9 shows yet another preferred embodiment of a fixing clamp.

Yet another fixing clamp 71 differs from the another fixing clamp 62shown in FIGS. 7 and 8 in that the yet another fixing clamp 71 hasraised portions (curved portions) 72 between an opening of the holdingportion 63 and the mounting or fixing portions 64. For the rest, the yetanother fixing clamp 71 has basically the same configuration as theanother fixing clamp 62. In the yet another fixing clamp 71, arelatively long and curved opening 73 or an opening 73 is definedbetween the opening of the holding portion 63 and the mounting portions64. When the fixing clamp 71 is deformed so as to join the mountingportions 64 together, both raised portions 72 are approached orcontacted each other to be joined together, the opening of the holdingportion 63 and the curved opening 73 are closed. Therefore, more stableretaining function is secured for the resin tube 14 when the fixingclamp 71 is fastened to or securely fixed in the motor vehicle body.

As stated above, according to the embodiment of the present invention,as there is no need to shape the resin tube 14 in a predetermined bentor curved shape in a manufacturing step, a cost related to the resintube 14 may be lowered.

And, the resin tube 14 is in the form of a straight tubular shape untilassembled in the motor vehicle body. The resin tube 14 is bent or curvedin a required bent or curved shape just when assembled in the motorvehicle body in an assembling step. Therefore, there is no need toprepare varied types of the resin tubes 14 corresponding to types ofmotor vehicles or piping layouts, and a common type of the resin tube 14may be used for various types of motor vehicles or various pipinglayouts.

And, according to this embodiment, both side regions of each of the bentpoints 50 (50-1, 50-2, 50-3) of the resin tube 14 are held and securelyfixed in the motor vehicle body by fixing clamps 48, 62 (62 and 67) or71. So, when vibration is transmitted to the resin tube 14 from themotor vehicle body, oscillation or vibration of the resin tube 14 may berestrained small, and restraining or clamping action of the fixingclamps 48, 62 (62 and 67) or 71 does not allow rotational movement ofthe resin tube 14 itself. That is, the connector 16 does not relativelyrotate relative to the mating pipe 10. This may simultaneously solve theproblem that the O-ring 22 in the connector 16 is worn and collapsed dueto relative rotational movement of the resin tube 14 and thereby sealingproperty is lowered, and good sealing property between the connector 16and the mating pipe 10 may be maintained for a long time.

In this embodiment, a small diameter tube is adapted for the resin tube14, and the resin tube 14 is very flexible. Therefore, when the resintube 14 is bent in an assembling step, it is hard to be broken (kinked).The resin tube 14 may be easily bent and deformed in a bent shape asdesired and assembled in the motor vehicle body.

In the fixing clamps 48, 62, 71 of this embodiment, the resin tube 14may be fitted in the C-shaped holding portions 54, 63 by resilientlyopening or widening the C-shaped holding portions 54, 63. Therefore, anoperator can easily fasten the resin tube 14 to the motor vehicle bodyby means of fixing clamps 48, 62, 71 while bending the resin tube 14 inan assembling site.

The fixing clamps 62 and 71 according to the present invention haveopenings 65, 73 before clamped, which are closed when fastened to orsecurely fixed in the motor vehicle body. This configuration may reduceor eliminate a clearance relative to the resin tube 14, and therebyfavorably restrains the resin tube 14 from oscillation. Therefore, theseclamps are preferable, but in the present invention, also adaptable arefixing clamps of varied configurations in addition to the fixing clamps48, 62, 71 described above.

As stated above, FIG. 4 shows the resin tube 14 before assembled in themotor vehicle body. As understood from the figure, the resin tube 14 hasa straight tubular shape before assembled. That is, the resin tube 14 isformed or molded in the form of the straight tubular shape by extrusionor the like. The resin tube 14 is equipped with the connectors 16 onboth end portions of the resin tube 14 before assembled in the motorvehicle body, and the resin tube 14 with the connectors 16 thereon isassembled in the motor vehicle body.

The end portions of the resin tube 14 are expanded in a flared shape(flared out) before equipped with the connectors 16.

Flaring out of the end portion of the resin tube 14 permits the nippleportion 28 of the connector 16 to be force fitted favorably in the resintube 14, specifically, the resin tube body 14A.

At that time, as shown in FIG. 11 of a comparison example, if theclamped layer 14B is laminated to cover the resin tube body 14A up to aterminal end of the resin tube body 14A (refer to FIG. 11 (A)), as shownin FIG. 11 (B), when a flaring jig 74 is inserted inside the resin tubebody 14A to flare an end portion thereof, a flared portion 76 or aflared portion 76 of the resin tube body 14A contracts under a pressureexerted in an axial direction and so on, an end portion of the clampedlayer 14B overlies an end surface of the flared portion 76 as well shownin a fragmentary enlarged view of FIG. 11 (C). That is, an overlyingportion 78 is defined. As the case may be, a leading end of theoverlying portion 78 extends or protrudes beyond an inner surface of theterminal end of the flared portion 76 towards an axis.

Therefore, when the nipple portion 28 of the connector 16 is forcefitted in the resin tube body 14A in this state as shown in FIG. 11 (C),there is a fear that the overlying portion 78 scratches an O-ring 80that is fitted on an outer peripheral surface of the nipple portion 28,or the overlying portion 78 is caught in or jammed by the nipple portion28 and sealing property of the O-ring 80 is lowered.

According to this embodiment, before the connector 16 is force fitted inand equipped to the resin tube 14, the clamped layer 14B is firstlaminated on the resin tube body 14A so as to cover an entire length ofthe resin tube body 14A, from one end to the other end thereof (a firststep), as shown in FIG. 10 (A). Then, as shown in FIGS. 10 (B) and (C),the terminal end portion of the clamped layer 14B is cut and removed forpredetermined length.

Specifically, as understood from FIG. 10 (B), a cylindrical cuttingguard 84 that has a convergent end portion 82 is slid into between theresin tube body 14A and the clamped layer 14B for a certain axial lengthfrom the axial end of the resin tube 14 to protect or guard the resintube body 14A (a second step). Then, while protecting the resin tubebody 14A by the cutting guard 84, a cutting blade 86 is applied onto anouter peripheral surface of the clamped layer 14B, and the resin tube 14and the cutting blade 86 are rotated relatively so that an annular endpart or portion of the clamped layer 14B is cut by the cutting blade 86and removed from on the resin tube body 14A (a third step).

Relative rotation may be caused by rotating either the resin tube 14 orthe cutting blade 86. However, it bothers an operator to rotate thelengthy resin tube 14. So, it is preferred to rotate the cutting blade86 because cutting is easily applicable for the resin tube 14 of anylength.

In this manner, an end portion of the resin tube body 14A is exposedalong a predetermined length δ thereof as shown in FIG. 10 (C).

After that, a shown in FIG. 10 (D), the end portion of the resin tubebody 14A is flared and expanded radially outwardly by the flaring jig 74(a fourth step).

In this state, as shown in FIG. 10 (E), the nipple portion 28 of theconnector 16 is force fitted in the resin tube body 14A, and theconnector 16 is attached to an end portion of the resin tube 14 (a fifthstep).

During that time, as the end portion of the clamped layer 14B does notoverlies an end surface of the flared portion 76, namely the overlyingportion 78 as shown in FIG. 11 (C) is not defined, the O-ring 80 is notscratched when the nipple portion 28 is force fitted in the resin tubebody 14A. And, there occurs no problem that the overlying portion 78 iscaught in or jammed by the O-ring 80, etc. and sealing property of theO-ring 80 is lowered.

According to this embodiment of the present invention, when the resintube 14 is clamped by the fixing clamps 48, 62, 71, the clamped layer14B laminated on the outer peripheral surface of the resin tube body 14Aeffectively prevents the resin tube body 14A from being scratched.Accordingly, it is allowed to favorably assemble the resin tube 14 inthe motor vehicle body by clamping the resin tube 14 with the fixingclamps 48, 62, 71.

And, in this embodiment, the clamped layer 14B is provided on the resintube body 14A and along substantially an entire length of the resin tubebody 14A. So, the resin tube body 14A may be effectively prevented frombeing scratched when the resin tube 14 is clamped at any points thereofby the fixing clamps 48, 62, 71.

That means, according to this embodiment, the resin tube 14 may beclamped at any points thereof along an axial direction by the fixingclamps 48, 62, 71 without damaging the resin tube body 14A. Therefore,the resin tube 14 may be assembled in the motor vehicle body whileshaping the resin tube 14 in various bent shapes.

In this embodiment, the end portion of the clamped layer 14B is removedfor a predetermined length 6 from either end of the clamped layer 14B orthe resin tube body 14A so that either end portion of the resin tubebody 14A is exposed. So, the overlying portion 78 of the clamped layer14B is not defined when a terminal end or the end portion of the resintube body 14A is flared. This solves the problem that when the nippleportion 28 of the connector 16 is force fitted inside the resin tubebody 14A, the O-ring 80 fitted on an outer peripheral surface of thenipple portion 28 is damaged, or the overlying portion 78 is caught inor jammed by the O-ring 80 or the like and thereby a sealing property islowered.

According to the method for producing the resin tube 14 of thisembodiment, first, the clamped layer 14B is laminated so as to cover theresin tube body 14A along an entire length from one end to the other endthereof, then, the cylindrical cutting guards 84 are slid between theresin tube body 14A and the clamped layer 14B from either longitudinalend thereof, respectively, end portions of the clamped layer 14B areannularly cut by the cutting blade 86, while protecting the resin tubebody 14A by the cutting guards 84 and removed. In this manner, bothannular end portions of the clamped layer 14B of a predetermined lengthmay be removed favorably from an outer peripheral surface of the resintube body 14A without damaging the resin tube body 14A.

Meanwhile, in this embodiment, a mark 88 is provided on an outerperipheral surface of the resin tube 14, specifically on an outerperipheral surface of the clamped layer (protective layer) 14B, linearlyin a longitudinal direction of the resin tube 14 in a state that theresin tube 14 extends straight as shown in FIG. 4 (C).

In this embodiment, the mark 88 is configured by arranging letters,numbers and transverse lines. Needless to say, the mark 88 may beconfigured by arranging other letters, numbers and other symbolslinearly. The mark 88 is provided, for example, on the outer peripheralsurface of the resin tube 14, so as to have a width in a range ofone-twentieth to one-fifth of an outer perimeter of the resin tube 14(for example, in a range of one-fourteenth to one tenth of the outerperimeter of the resin tube 14). For example, when the resin tube 14 hasan outer diameter of 6 mm, the mark 88 may have a height in a range ofabout 0.9 mm to about 3.8 mm (for example, in a range of about 1.3 mm toabout 1.9 mm). Here, for example, the mark 88 is designed to have aheight of 1.5 mm. The mark 88 is not necessary to have a width in arange of one-twentieth to one-fifth of a circumference of the resin tube14 (for example, in a range of one-fourteenth to one-tenth of thecircumference of the resin tube 14) along an entire length thereof, butthe mark 88 is sufficient to have such width on a major part thereof, oron a major part thereof along the longitudinal direction thereof. Inthis configuration, the mark 88 has a proper width, and thereby kinkpreventive effect may be improved.

The resin tube 14 in a form of straight tubular shape shown in FIG. 4(A) is entirely provided with a predetermined bent shape when assembledin the motor vehicle body as shown in FIG. 1.

During assembling, the resin tube 14 is bent or deformed in a bent shapewithout producing kinks in the marks 88 about an axis of the resin tube14 and is fastened to or securely fixed in the motor vehicle body by thefixing clamps 48, 62, 71.

In the embodiment as stated above, when the resin tube 14 is kinkedduring assembling in the motor vehicle body, kinks are produced in themark 88 arranged linearly as well as in the resin tube 14 itself.Therefore, an operator can easily and visually verify by the mark 88that kinks are produced in the resin tube 14.

So, according to this embodiment, the resin tube 14 should be arrangedand assembled in the motor vehicle body so as to maintain a lineararrangement of the mark 88. In this manner, an operator can arrange andassemble the resin tube 14 without producing kinks in the resin tube 14.

That means, it may be prevented that a high stress is generated inkinked portions of the resin tube 14, and deterioration of the resintube 14 is progresses by the stress. Further, it also may be preventedthat due to the kinks of the resin tube 14, the sealing member such asO-ring 22 of the connector 16 partially contacts the mating pipe 10 andthereby sealing property is lowered.

Meanwhile, for example, when the connector 300 (the retainer 302 isunitary incorporated in the retainer holding portion 304) is adapted inthe embodiment of the present invention, the mark 88 is preferablyprovided on the resin tube 14 so as to correspond to one or the otherpress portion 324 (an operating direction of one or the other pressportion 324), or so as to conform or generally conform to the one or theother press portion 324 relative to a circumferential position. Withthis configuration, in case that an operator is hard to visually findthe operating portion (press portion 324), for example, the operatingportion is housed in the connector body 306 (refer to FIG. 16), and theconnector 300 is located in a region where parts and components areclosely arranged, the operator can find the operating portion with aclue of the mark 88 that is arranged on the resin tube 14 so as tocorrespond to the operating portion.

When the connector 16 is adapted, as shown in FIG. 4 (D), the checkermember 90 may be mounted or installed on the retainer holding portion 26for verifying complete connection between the connector 16 and themating pipe 10. The checker member 90 is constructed in a followingmanner. The checker member 90 is mounted or installed on the retainerholding portion 26 such that stop claws 94 of resilient arms 92 enter inthe opening windows 30 of the retainer holding portion 26 while engagingwith circumferential edge portions 96 of the opening windows 30 (in amounted state, the stop claws 94 enter inside the engaging recessedportions or engaging slit portions 34 of the retainer 20). When themating pipe 10 is inserted within the retainer 20, and connected to theconnector body 18 correctly, the engaging projection 12 pushes the stopclaws 94 radially outwardly, engagement of the stop claws 94 with theopening windows 30 is cancelled. And, the checker member 90 may beremoved from the connector 16 by pulling in a direction indicated by anarrow (in a direction perpendicular to a planar portion 98 between theopening windows 30 of the retainer holding portion 26). So, completeconnection between the mating pipe 10 and the connector 16 may beverified by removing the checker member 90. In this case, the mark 88may be provided on the resin tube 14 so as to correspond to a removing(a mounting and removing) direction of the checker member 90, or aremoving (a mounting and removing) side of the checker member 90 (incase shown in FIG. 4 (D)) relative to a circumferential position.Namely, the mark 88 may be provided on the resin tube 14 so as to belocated between the opening windows 30 relative to a circumferentialposition. Or the mark 88 may be provided on the resin tube 14 so as toconform to or generally conform to between the opening windows 30 or theplanar portion 98 relative to a circumferential position, and at a sidewhere the checker 90 is mounted. Further, the mark 88 may be provided onthe resin tube 14 so as to correspond to a diametrically opposite sideor diametrically symmetrical side to the removing (the mounting andremoving) direction of the checker 90, or the removing (the mounting andremoving) side of the checker member 90 relative to a circumferentialposition ( at 180° opposite to the position shown in FIG. 4 (D)). Inthis construction, an operator can arrange the resin tube 14 such thatthe checker member 90 is arranged in such orientation as to allowhim/her to remove the checker 90 from the connector 16 by checking themark 88. Or, for example, when the connector 400 (when the mating pipe202 is completely inserted in the connector 400, the retainer 402 isallowed to be pushed relative to the retainer holding portion 404) isadapted in the embodiment of the present invention, the mark 88 issimilarly provided on the resin tube 14 on the basis of a removingdirection or a removing side of the checker member 406. For example,with reference to FIG. 18 (B) just for the sake of convenience, thechecker member 406 is removed in a direction indicated by an arrow. Themark 88 may be provided on the resin tube 440 so as to correspond tothis removing direction (the removing side or the mounting and removingside) relative to a circumferential position (refer to a circumferentialposition indicated by reference numeral 442). Meanwhile, a positioncorresponding to diametrically symmetrical position of the removingdirection (the removing side or the mounting and removing side) of thechecker member 406 relative to a circumferential position is acircumferential position 180° opposite to the circumferential positionindicated by reference numeral 442 (lower position in the figure).

Although the preferred embodiments have been described above, these areonly some of embodiments of the present invention.

For example, the marks 88 may take various forms other than the above.Or, as the case may be, it is possible to adapt the present invention toa resin tube having an outer diameter greater than 6 mm. Further, aconnector, which has a retainer that is deformable resiliently in aradial direction, may be adapted for being attached to each of both endportions or one of the both end portions of the resin tube 14. Theretainer may be configured separately from, unitary with or integrallywith a connector body. In the connector that is used in embodimentsaccording to the present invention, when the mating pipe 10 is insertedin the connector body, the retainer is pushed by the engaging projection12 of the mating pipe 10, is deformed once in a radial direction (forexample, deformed so as to expand in the radial direction), then isreturned resiliently to its original shape to engage with the engagingprojection 12 of the mating pipe 10. As a result, the connector body issecurely fixed with the mating pipe 10 in an axial direction. When theconnector 300 or the connector 400 is adapted, the connecting portion312 or the connecting portion 414 is configured suitably to be fitted inthe resin tube 14 (for example, as a force-fit portion).

As stated, the present invention may be constructed and embodied invarious configurations and modes within the scope of the presentinvention.

1. A piping structure for transporting a fuel, arranged between anengine and a fuel tank, comprising: a resin tube formed in a straighttubular shape, for transporting a fuel, the resin tube being flexed andbent at one or more points along a longitudinal direction of the resintube to define one or more bent portions and thereby being provided witha predetermined bent shape, and a fixing clamp for fixing the resin tubein a motor vehicle body so as to retain the one or more bent portionsand thereby assembling the resin tube in the motor vehicle body.
 2. Thepiping structure for transporting a fuel as set forth in claim 1,further comprising: a connector attached to an end portion of the resintube for connecting the resin tube with a mating pipe, and the resintube being assembled in the motor vehicle body while being connectedwith the mating pipe via the connector.
 3. The piping structure fortransporting a fuel as set forth in clam 2, wherein the fixing clampretains the one or more bent portions of the resin tube by fixing aregion of each side of the one or more bent portions of the resin tubein the motor vehicle body.
 4. The piping structure for transporting afuel as set forth in claim 2, wherein the resin tube has a small outerdiameter up to 6 mm.
 5. The piping structure for transporting a fuel asset forth in claim 2, wherein the mating pipe is integrally formed in acomponent that is securely fixed in the motor vehicle body.
 6. Thepiping structure for transporting a fuel as set forth in claim 4,wherein the engine is connected to a rear wheel so as to fluctuate alongwith the rear wheel.
 7. The piping structure for transporting a fuel asset forth in claim 2, wherein the fixing clamp has a generally annularholding portion, and an opening through which the resin tube is fittedin the holding portion in a direction perpendicular to an axis, thefixing clamp is constructed such that the opening is closed when thefixing clamp is fixed in the motor vehicle body while holding the resintube in the holding portion.
 8. The piping structure for transporting afuel as set forth in claim 2 wherein the connector has; a) a connectorbody in a form of a cylindrical shape as a whole, including a retainerholding portion on one end of the connector body along an axialdirection and a connecting portion on the other end of the connectorbody for being connected to the resin tube, b) a retainer held in or onthe retainer holding portion for engaging with a pipe side engagingportion in a form of a projection or recess on an outer peripheralsurface of the mating pipe, and at a position spaced apart from an axialend of an inserting end portion of the mating pipe, c) a sealing memberplaced inside the other end of the connector body relative to theretainer holding portion, wherein the retainer securely fixes the matingpipe that is inserted in the connector body in an axial direction, thesealing member contacts with an outer peripheral surface of theinserting end portion of the mating pipe that is inserted in theconnector body to provide a seal relative to the inserting end portionthereof.
 9. The piping structure for transporting a fuel as set forth inclaim 8 wherein the retainer holding portion is in a form of a socketshape, and the connecting portion is configured as a force-fit portionto be force fitted inside the resin tube.
 10. A resin tube fortransporting a fuel to be adapted in a piping structure for transportinga fuel, arranged between an engine and a fuel tank, the pipingstructure, comprising: a resin tube formed in a straight tubular shape,for transporting a fuel, the resin tube being flexed and bent at one ormore points along a longitudinal direction of the resin tube to defineone or more bent portions and thereby being provided with apredetermined bent shape, and a fixing clamp for fixing the resin tubein a motor vehicle body so as to retain the one or more bent portionsand thereby assembling the resin tube in the motor vehicle body, theresin tube, comprising: a small diameter resin tube body with an outerdiameter up to 6 mm, and an elastic clamped layer laminated on an outerperipheral surface of the resin tube body to be clamped by the fixingclamp, the elastic clamped layer having a predetermined wall thicknessand covering the resin tube body along an entire effective length of theresin tube that effects flexing deformation.
 11. The resin tube fortransporting a fuel as set forth in claim 10, wherein the clamped layeris formed with wall-thickness in a range of 0.7 to 1.3 mm.
 12. The resintube for transporting a fuel as set forth in claim 10, wherein the resintube is connected with a mating pipe via a connector, the connectorincludes a tubular nipple portion as a fit-in portion for being fittedin the resin tube, the tubular nipple portion is provided with anannular sealing member such as O-ring on an outer peripheral surface ofthe tubular nipple portion, wherein the clamped layer is removed forpredetermined length from an extremity of the resin tube body so as toexpose an end portion of the resin tube body.
 13. The resin tube fortransporting a fuel as set forth in claim 10, wherein an end portion ofthe clamped layer is removed for a length of 2 to 8 mm from theextremity of the resin tube body.
 14. A resin tube for transporting afuel to be adapted in a piping structure for transporting a fuel,arranged between an engine and a fuel tank, the piping structure,comprising: a resin tube formed in a straight tubular shape, fortransporting a fuel, the resin tube being flexed and bent at one or morepoints along a longitudinal direction of the resin tube to define one ormore bent portions and thereby being provided with a predetermined bentshape, and a fixing clamp for fixing the resin tube in a motor vehiclebody so as to retain the one or more bent portions and therebyassembling the resin tube in the motor vehicle body, wherein a mark isprovided on an outer peripheral surface of the resin tube, along agenerally entire length of the resin tube, the mark extends linearly ina longitudinal direction of the resin tube in a state that the resintube extends straight.
 15. The resin tube for transporting a fuel as setforth in claim 14, wherein the resin tube has a small outer diameter upto 6 mm.
 16. The resin tube for transporting a fuel as set forth inclaim 14, wherein the resin tube is connected with a mating pipe via aconnector, and the connector is configured to be sealed relative to amating pipe by an annular sealing member such as an O-ring andconfigured to be rotatable relative to the mating pipe.
 17. The resintube for transporting a fuel as set forth in claim 14, wherein aconnector is attached to an end portion of the resin tube for connectingthe resin tube with a mating pipe, and the connector is provided with achecker member for verifying complete connection with the mating pipe,wherein the mark is provided on the resin tube so as to correspond to amounting and removing direction of the checker member or a mounting andremoving side of the checker member relative to a circumferentialposition, or correspond to a diametrically opposite side to the mountingand removing direction of the checker member or the mounting andremoving side of the checker member relative to a circumferentialposition.
 18. The resin tube for transporting a fuel as set forth inclaim 14, wherein a connector is attached to an end portion of the resintube for connecting the resin tube with a mating pipe, the connector isprovided with a retainer for engaging with the mating pipe, the retainerhas an operating portion that does not project radially from theconnector, the operating portion is configured so as to cancelengagement of the mating pipe with the connector or with the retainer bybeing operated, wherein the mark is provided on the resin tube so as tocorrespond to the operating portion or an operating direction of theoperating portion relative to a circumferential position.